Hydraulic shovel

ABSTRACT

A hydraulic shovel ( 1 ) in which a vehicle body ( 2 ) is provided revolvably on a traveling body ( 6 ) includes a boom ( 3 ) connected rotatably to the vehicle body ( 2 ), an arm ( 4 ) connected rotatably to the boom ( 3 ), a bucket ( 5 ) connected rotatably to the arm ( 4 ), a boom hydraulic cylinder ( 10 ) that drives the boom ( 3 ), an arm hydraulic cylinder ( 9 ) that drives the arm ( 4 ), a bucket hydraulic cylinder ( 8 ) that drives the bucket ( 5 ), and a boom control valve ( 15 ), an arm control valve ( 35 ) and a bucket control valve ( 45 ) which respectively control a flow of a working oil supplied to and discharged from the respective hydraulic cylinders ( 8, 9, 10 ), wherein the boom ( 3 ) is formed to be hollow, and the bucket control valve ( 45 ) is disposed in an interior of the boom ( 3 ).

TECHNICAL FIELD

This invention relates to a hydraulic shovel in which a front attachment constituted by a boom, an arm, and a bucket is driven by a hydraulic cylinder.

BACKGROUND ART

In a conventional hydraulic shovel, discretely disposed control valves are provided in the front attachment, and a flow of working oil supplied to and discharged from respective hydraulic cylinders is controlled by the respective control valves (see JP2004-293089A and JP2005-68718A).

In the hydraulic shovel disclosed in JP2004-293089A, the control valves are disposed in the vicinity of the respective hydraulic cylinders that drive the front attachment.

In the hydraulic shovel disclosed in JP2005-68718A, the control valves are disposed in series on an outer side of the boom.

DISCLOSURE OF THE INVENTION

However, in this type of conventional hydraulic shovel, the control valves are provided on the front attachment, and therefore the weight balance of the front attachment deteriorates due to the weight of the control valves.

Furthermore, the control valves are provided on the outside of the front attachment, and therefore the control valves, pipes thereof, and so on may be damaged through contact with an obstruction during an operation.

This invention has been designed in consideration of these problems, and it is an object thereof to provide a hydraulic shovel with which the weight balance of a front attachment can be improved and damage to control valves and pipes can be prevented.

This invention is a hydraulic shovel in which a vehicle body is provided revolvably on a traveling body. The hydraulic shovel comprises a boom connected rotatably to the vehicle body, an arm connected rotatably to the boom, a bucket connected rotatably to the arm, a boom hydraulic cylinder that drives the boom, an arm hydraulic cylinder that drives the arm, a bucket hydraulic cylinder that drives the bucket, and a boom control valve, an arm control valve and a bucket control valve which respectively control a flow of a working oil supplied to and discharged from the respective hydraulic cylinders, wherein the boom is formed to be hollow, and the bucket control valve is disposed in an interior of the boom.

According to this invention, the weight of the bucket control valve is not applied to the arm, and therefore the weight balance of the front attachment improves, leading to an improvement in the operational stability of the front attachment. Furthermore, damage to the bucket control valve and pipes or the like connected thereto through contact with an obstruction is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing a hydraulic shovel according to an embodiment of this invention.

FIG. 2 shows a hydraulic circuit for supplying and discharging working oil to and from a bucket hydraulic cylinder.

BEST MODES FOR CARRYING OUT THE INVENTION

An embodiment of this invention will be described below with reference to the drawings.

As shown in FIG. 1, in a hydraulic shovel (construction machine) 1 according to an embodiment of this invention, a vehicle body (revolving body) 2 is provided revolvably on an upper portion of a traveling body 6.

The hydraulic shovel 1 includes a boom 3 connected rotatably to the vehicle body 2 via a boom support shaft 7, two boom hydraulic cylinders 10 for driving the boom 3, an arm 4 connected rotatably to a tip end of the boom 3 via an arm support shaft 38, an arm hydraulic cylinder 9 for driving the arm 4, a bucket 5 connected rotatably to a tip end of the arm 4 via a bucket support shaft 51, and a bucket hydraulic cylinder 8 for driving the bucket 5.

An oil pressure supply unit 21 is installed in the vehicle body 2. The hydraulic cylinders 8-10 are caused to expand and contract by working oil introduced from the oil pressure supply unit 21. By causing the hydraulic cylinders 8-10 to expand and contract, the bucket 5, arm 4, and boom 3 are respectively rotated, whereby the hydraulic shovel performs operations such as ground excavation and earth transportation.

An articulated front attachment is constituted by the boom 3, arm 4, and bucket 5. It should be noted that the bucket 5 connected to the tip end of the arm 4 is not limited to ground excavation and earth transportation operations, and may perform other operations.

The boom hydraulic cylinders (actuators) 10 provided in a pair are disposed on either side of the boom 3. Each boom hydraulic cylinder 10 expands and contracts when a piston rod 12 is moved relative to a cylinder tube 11 by an oil pressure received by a piston (not shown) provided in the interior of the boom hydraulic cylinder 10. A base end portion of each cylinder tube 11 is connected rotatably to the vehicle body 2 via a support shaft 13, while a tip end portion of each piston rod 12 is connected rotatably to the boom 3 via a support shaft 14. The two boom hydraulic cylinders 10 drive the boom 3 by expanding and contracting synchronously in accordance with working oil pressure supplied and discharged via a control valve 15.

The arm hydraulic cylinder (actuator) 9 that drives the arm 4 is disposed on a back portion of the boom 3. The arm hydraulic cylinder 9 expands and contracts when a piston rod 32 is moved relative to a cylinder tube 31 by an oil pressure received by a piston (not shown). A base end portion of the cylinder tube 31 is connected rotatably to the boom 3 via a support shaft 33, while a tip end portion of the piston rod 32 is connected rotatably to the arm 4 via a support shaft 34. The arm hydraulic cylinder 9 drives the arm 4 by expanding and contracting in accordance with working oil pressure supplied and discharged via a control valve 35.

The bucket hydraulic cylinder (actuator) 8 that drives the bucket 5 is disposed on a back portion of the arm 4. A base end portion of a cylinder tube 41 is connected rotatably to the arm 4 via a support shaft 43, while a tip end portion of a piston rod 42 is connected rotatably to the bucket 5 via a support shaft 44.

FIG. 2 shows a hydraulic circuit for supplying and discharging working oil to and from the bucket hydraulic cylinder 8.

The piston rod 42 is inserted into the cylinder tube 41 of the bucket hydraulic cylinder 8 to be free to advance and retreat, and a piston 46 is connected to a base end portion of the piston rod 42. The piston 46 is interposed into an inner periphery of the cylinder tube 41 to be free to slide, and divides the interior of the cylinder tube 41 into an anti rod-side oil chamber 47 and a rod-side oil chamber 48. The working oil is supplied to and discharged from the anti rod-side oil chamber 47 and the rod-side oil chamber 48 via a control valve 45, and the bucket hydraulic cylinder 8 drives the bucket 5 by expanding and contracting in accordance with the pressure of this working oil.

The control valve 45 is constituted by four solenoid valves V1 to V4 interposed into a bridge circuit. The solenoid valves V1 to V4 are opened and closed in accordance with an output signal from a controller 30, thereby causing the hydraulic cylinder 8 to expand and contract.

A supply passage 25 through which the working oil to be supplied to the hydraulic cylinder 8 flows is connected to a discharge side of a hydraulic pump 22, and the supply passage 25 is connected to branch passages 26, 27 that bifurcate in two directions. The branch passages 26, 27 then re-converge so as to join a return passage 23 through which the working oil that is discharged from the hydraulic cylinder 8 flows. The return passage 23 is connected to a suction side of the hydraulic pump 22.

A meter-in solenoid valve V1 that controls the flow of the working oil supplied to the anti rod-side oil chamber 47 of the hydraulic cylinder 8 and a meter-in solenoid valve V3 that controls the flow of the working oil supplied to the rod-side oil chamber 48 are interposed in parallel in the branch passages 26, 27.

Further, a meter-out solenoid valve V2 that controls the flow of the working oil discharged from the anti rod-side oil chamber 47 of the hydraulic cylinder 8 and a meter-out solenoid valve V4 that controls the flow of the working oil discharged from the rod-side oil chamber 48 are interposed in parallel in the branch passages 26, 27.

Hence, the meter-in solenoid valve V1 and the meter-out solenoid valve V2 are interposed in series in the branch passage 26, while the meter-in solenoid valve V3 and the meter-out solenoid valve V4 are interposed in series in the branch passage 27.

A first supply/discharge passage 28 that communicates with the anti rod-side oil chamber 47 is connected between the meter-in solenoid valve V1 and the meter-out solenoid valve V2 in the branch passage 26. A second supply/discharge passage 29 that communicates with the rod-side oil chamber 48 is connected between the meter-in solenoid valve V3 and the meter-out solenoid valve V4 in the branch passage 27.

The meter-in solenoid valve V1, meter-out solenoid valve V2, meter-in solenoid valve V3, and meter-out solenoid valve V4 are solenoid control valves (flow control valves). Each solenoid valve V1 to V4 is driven by a control current output from the controller 30 such that an opening area thereof is adjusted in accordance with the control current. Hence, the controller 30 adjusts the opening areas of the respective solenoid valves V1 to V4 individually such that the flow of the working oil passing through the respective solenoid valves V1 to V4 is controlled individually. Signals from pressure sensors 18, 19 that detect the pressure in the first supply/discharge passage 28 and the second supply/discharge passage 29, respectively, are input into the controller 30.

The boom control valve 15 and the arm control valve 35 are constituted similarly to the bucket control valve 45, and are controlled by control currents output from the controller 30. Hence, in the hydraulic shovel 1, the respective control valves 15, 35, 45 can be disposed discretely.

In a conventional hydraulic shovel, the discretely disposed control valves are provided in the vicinity of the respective hydraulic cylinders in an attempt to reduce the length of hydraulic pipes connecting the control valves to the hydraulic cylinders.

However, when the bucket control valve is provided in the vicinity of the bucket hydraulic cylinder, the weight balance of the front attachment constituted by the boom, arm, and bucket deteriorates due to the weight of the bucket control valve. In other words, a center of gravity of the hydraulic shovel 1 shifts forward, causing the hydraulic shovel 1 to become unstable.

Furthermore, when the bucket control valve is provided in the vicinity of the bucket hydraulic cylinder, the bucket control valve moves together with the arm, and therefore the bucket control valve and pipes or the like connected thereto may be damaged through contact with an obstruction.

In response to this problem, this invention improves the weight balance of the front attachment and prevents damage to the bucket control valve 45 and pipes connected thereto by providing the discretely disposed bucket control valve 45 in the interior of the boom 3.

In this embodiment, the discretely disposed control valves 15, 35, 45 are all provided in the interior of the boom 3.

The boom 3 is formed in a hollow box shape from steel plate, and the respective control valves 15, 35, 45 are accommodated in an interior space thereof. Each control valve 15, 35, 45 is supported via a support member (not shown).

The control valves 15, 35, 45 are disposed above the boom support shaft 7 that supports the boom 3 rotatably on the vehicle body 2. More specifically, each control valve 15, 35, 45 is disposed in a higher position than the boom support shaft 7, which serves as a rotary axis of the front attachment, regardless of a rotation position of the boom 3, and each control valve 15, 35, 45 is disposed so as to be positioned vertically above the boom support shaft 7 in accordance with the rotation position of the boom 3. As a result, a force generated in a rotation direction of the front attachment weakens. In other words, the weight balance of the front attachment improves, leading to operational stability.

Each control valve 15, 35, 45 is accommodated in a rear portion of the boom 3, or in other words a position close to a revolving central axis O of the vehicle body 2. As a result, a free end side of the front attachment decreases in weight and a side thereof close to the vehicle body 2 increases in weight. Thus, the weight balance of the front attachment improves, leading to operational stability. Furthermore, the center of gravity of the hydraulic shovel 1 is positioned close to the revolving central axis O, and therefore the traveling stability of the hydraulic shovel 1 also improves. It should be noted that in the boom 3, a direction extending from the boom support shaft 7 to the arm support shaft 38 forms the front of the boom 3 and an opposite direction thereto forms the rear of the boom 3.

As shown in FIG. 1, the bucket control valve 45 is preferably disposed vertically above the boom support shaft 7 in a state where the boom hydraulic cylinders 10 are positioned in near a neutral state. By disposing the bucket control valve 45 in this manner, the weight balance of the front attachment is improved even further.

The control valves 15, 35, 45 are disposed in series in a front-rear direction of the boom 3. The bucket control valve 45 is disposed between the boom control valve 15 and the arm control valve 35. The boom control valve 15 is disposed to the rear of the bucket control valve 45, and the arm control valve 35 is disposed to the front of the bucket control valve 45.

Supply/discharge passages 16, 17, 36, 37, 28, 29 extending respectively from the control valves 15, 35, 45 to the hydraulic cylinders 10, 9, 8 are partially accommodated in the interior of the boom 3.

The hydraulic shovel 1 constituted as described above causes the hydraulic cylinders 10, 9, 8 to expand and contract by switching supply and discharge of the working oil to and from the hydraulic cylinders 10, 9, 8 through the respective control valves 15, 35, 45. As a result, the articulated front attachment constituted by the boom 3, arm 4, and bucket 5 is driven to perform ground excavation and earth transportation operations via the bucket 5 connected to the tip end of the arm 4.

According to the embodiment described above, the following effects are obtained.

The bucket control valve 45 is disposed in the interior of the hollow box-shaped boom 3, and therefore the weight of the bucket control valve is not applied to the arm 4. Hence, the weight balance of the front attachment improves, leading to an improvement in the operational stability of the front attachment. Furthermore, damage to the bucket control valve 45 and pipes or the like connected thereto through contact with an obstruction can be prevented.

Moreover, the bucket control valve 45 is disposed above the boom support shaft 7, thereby improving the weight balance of the front attachment and leading to operational stability.

Furthermore, the boom control valve 15 and the arm control valve 35 are disposed in the interior of the boom 3 in series with the bucket control valve 45, leading to a further improvement in the weight balance of the front attachment. Hence, operations of the front attachment are stabilized, and damage to the respective control valves 45, 15, 35 and pipes or the like connected thereto is prevented.

Further, the bucket control valve 45 is constituted by the solenoid valves V1 to V4 which are opened and closed individually by a control current output from the controller 30, and therefore the bucket control valve 45 can be disposed in the interior of the boom 3 without disposal constraints.

This invention is not limited to the embodiment described above, and may be subjected to various modifications within the scope of the technical spirit thereof.

INDUSTRIAL APPLICABILITY

This invention may be applied to a hydraulic shovel that performs operations such as ground excavation and earth transportation. 

1. A hydraulic shovel (1) in which a vehicle body (2) is provided revolvably on a traveling body (6), comprising: a boom (3) connected rotatably to the vehicle body (2); an arm (4) connected rotatably to the boom (3); a bucket (5) connected rotatably to the arm (4); a boom hydraulic cylinder (10) that drives the boom (3); an arm hydraulic cylinder (9) that drives the arm (4); a bucket hydraulic cylinder (8) that drives the bucket (5); and a boom control valve (15), an arm control valve (35) and a bucket control valve (45) which respectively control a flow of a working oil supplied to and discharged from the respective hydraulic cylinders (8, 9, 10), wherein the boom (3) is formed to be hollow, and the bucket control valve (45) is disposed in an interior of the boom (3).
 2. The hydraulic shovel as defined in claim 1, further comprising a boom support shaft (7) that supports the boom (3) rotatably on the vehicle body (2), wherein the bucket control valve (45) is disposed above the boom support shaft (7).
 3. The hydraulic shovel as defined in claim 2, wherein the boom control valve (15) and the arm control valve (35) are disposed in the interior of the boom (3) in series with the bucket control valve (45).
 4. The hydraulic shovel as defined in claim 1, wherein an anti rod-side oil chamber (47) and a rod-side oil chamber (48) defined by a piston (46) are provided in an interior of the bucket hydraulic cylinder (8), and the bucket control valve (45) comprises: a first meter-in solenoid valve (V1) that controls the flow of the working oil supplied to the anti rod-side oil chamber (47); a first meter-out solenoid valve (V2) that controls the flow of the working oil discharged from the anti rod-side oil chamber (47); a second meter-in solenoid valve (V3) that controls the flow of the working oil supplied to the rod-side oil chamber (48); a second meter-out solenoid valve (V4) that controls the flow of the working oil discharged from the rod-side oil chamber (48); and a controller (30) that controls the flow of the working oil passing through the respective meter-in solenoid valves (V1, V3) and the respective meter-out solenoid valves (V2, V4) individually. 